Smith R M, Osborne-White W S, Russell G R
Biochem J. 1967 Aug;104(2):441-9. doi: 10.1042/bj1040441.
Experiments were conducted with aged nuclear-free homogenate of sheep liver and aged mitochondria in an attempt to measure both the extent of oxidation of propionate and the distribution of label from [2-(14)C]propionate in the products. With nuclear-free homogenate, propionate was 44% oxidized with the accumulation of succinate, fumarate, malate and some citrate. Recovery of (14)C in these intermediates and respiratory carbon dioxide was only 33%, but additional label was detected in endogenous glutamate and aspartate. With washed mitochondria 30% oxidation of metabolized propionate occurred, and proportionately more citrate and malate accumulated. Recovery of (14)C in dicarboxylic acids, citrate, alpha-oxoglutarate, glutamate, aspartate and respiratory carbon dioxide was 91%. The specific activities of the products and the distribution of label in the carbon atoms of the dicarboxylic acids were consistent with the operation solely of the methylmalonate pathway together with limited oxidation of the succinate formed by the tricarboxylic acid cycle via pyruvate. In a final experiment with mitochondria the label consumed from [2-(14)C]propionate was entirely recovered in the intermediates of the tricarboxylic acid cycle, glutamate, aspartate, methylmalonate and respiratory carbon dioxide.
实验采用了老龄绵羊肝脏的无细胞核匀浆和老龄线粒体，旨在测定丙酸盐的氧化程度以及[2-(14)C]丙酸盐中的标记物在产物中的分布情况。对于无细胞核匀浆，丙酸盐有44%被氧化，同时积累了琥珀酸、富马酸、苹果酸和一些柠檬酸。这些中间产物和呼吸二氧化碳中(14)C的回收率仅为33%，但在内源性谷氨酸和天冬氨酸中检测到了额外的标记物。对于洗涤后的线粒体，代谢的丙酸盐有30%发生氧化，且积累的柠檬酸和苹果酸比例更高。二羧酸、柠檬酸、α-酮戊二酸、谷氨酸、天冬氨酸和呼吸二氧化碳中(14)C的回收率为91%。产物的比活性以及二羧酸碳原子中标记物的分布与仅通过丙二酸单酰途径以及三羧酸循环经丙酮酸形成的琥珀酸的有限氧化作用相一致。在最后一个关于线粒体的实验中，[2-(14)C]丙酸盐消耗的标记物完全在三羧酸循环的中间产物、谷氨酸、天冬氨酸、丙二酸单酰和呼吸二氧化碳中回收。
